Well-known antimicrobial compositions include conventional treatments such as antiseptics and antibiotics. Other treatments include silver-containing gels, compounds containing heavy metals and solutions of hydrogen peroxide and natural and synthetic pharmaceutically active substances. However, treatments such as antibiotics have disadvantages because of the emergence of antibiotic resistance. Furthermore, high levels of hydrogen peroxide have a toxic effect. In addition, hydrogen peroxide in solution is typically unstable and it is difficult to provide a sustained delivery system for this material. Thus, for a wide variety of different reasons, conventional antimicrobial treatments have many drawbacks.
Additionally, there are a number of naturally occurring antimicrobial systems known which rely on the ability of certain oxidising agents to disrupt metabolic processes of bacteria, fungi and viruses. For example, WO 03/090800 is directed to wound dressings comprising hydrated hydrogels and enzymes. Specifically, this patent describes the need to keep the enzyme substrate physically separated from the oxidoreductase enzyme prior to the use of the dressing. This prevents an unwarranted reaction which according to WO 03/090800 is undesirable. Thus, the wound dressing of WO 03/090800 can only function when it has been used or applied to a wound i.e. after it has been brought in contact with an appropriate enzyme substrate.
Additionally, in recent years there has been a resurgence of interest in the therapeutic efficacy of honey, particularly in the area of wound healing. As a natural product, honey offers an attractive alternative to conventional treatments. Even though honey has been used for hundreds of years as a treatment for wounds, it is only relatively recently that the antibacterial properties of honey have been researched. This research has postulated that the antibacterial activity of honey is due to several key properties including high osmotic pressure, low water content, available water (Aw), low pH resulting in an acidic environment, glucose oxidase system which results in the formation of hydrogen peroxide, low protein content, high carbon to nitrogen ratio, low redox potential (Eh) due to high content of reducing sugars, chemical agents, pinocembrin, lysozyme, acids (phenolic), terpenes, benzyl alcohol and/or volatile substances (possibly phytochemicals influenced by bee enzymes).
Many different types of honey have antimicrobial activity. Over the past number of years Manuka honey has been recognised as having superior activity to most other honeys. Manuka honey is derived from the Manuka tree, Leptospermum scoparium, a native of New Zealand. Manuka honey is known for the treatment of wound infections and its antibacterial activity. It is the common perception in the field that Manuka contains a unique antibacterial factor and there is a wide body of research conducted to attempt to characterise this antimicrobial substance. Manuka honey has in recent years been tested in order to determine and quantify this antibacterial activity and unique antibacterial factor. Researchers in this field have found that when Manuka honey was subjected to catalase neutralization assays, where the amount of catalase added to Manuka honey samples was sufficient to destroy all hydrogen peroxide produced, antibacterial activity was still observed. This has resulted in the accepted perception in this field that there is a non-peroxide factor, referred to in the literature as Non-Peroxide Activity and Unique Manuka Factor (UMF), present in Manuka Honey causing this antibacterial activity. However, despite a significant amount of research aimed at identifying the substance(s) mediating the non-peroxide activity, or UMF, as yet, the precise nature of this activity is currently not known and no such substance has been clearly identified.
Some of the disadvantages associated with conventional treatments are outlined previously. Furthermore, natural honey as an antibacterial agent has several disadvantages. Firstly, natural honey is composed of a diverse mixture of identified and unidentified organic and inorganic compounds at various concentrations. In this respect it can be expected to demonstrate a degree of variability which may be unacceptable for its use in many clinical applications. Secondly, honey is mainly used for topical application. This is because when honey is diluted by, for example, absorption into the gut it becomes too diluted to have any detectable activity. Finally, honey is a natural product, which will have many additional compounds present and some of these compounds may give rise to an allergic reaction when it is applied. There is therefore a need for an antimicrobial system which overcomes the above-mentioned disadvantages and can provide antibacterial activity similar or better than natural honey. In particular, there is a need to carry out further research into the antibacterial role of Manuka honey in more detail in order to elucidate the mechanism of its antibacterial action.
Thus, there is therefore a need to research these conventional and natural treatments in order to generate further antimicrobial compositions which do not have the many disadvantages commonly associated with such treatments. Indeed, if the positive attributes of such conventional and natural treatments could be harnessed without the negative side effects or deleterious properties, this would result in a much improved alternative antibacterial system of significant medical and commercial importance.